Buggy code:
public final class CompletionEngine extends Engine implements ISearchRequestor , TerminalSymbols , TypeConstants { public static boolean DEBUG = false ; AssistOptions options ; CompletionParser parser ; ICompletionRequestor requestor ; ProblemReporter problemReporter ; char [ ] source ; boolean resolvingImports = false ; boolean insideQualifiedReference = false ; int startPosition ; int actualCompletionPosition ; int endPosition ; int offset ; HashtableOfObject knownPkgs = new HashtableOfObject ( 10 ) ; HashtableOfObject knownTypes = new HashtableOfObject ( 10 ) ; Scanner nameScanner ; static final char [ ] [ ] baseTypes = new char [ ] [ ] { "boolean" . toCharArray ( ) , "byte" . toCharArray ( ) , "char" . toCharArray ( ) , "double" . toCharArray ( ) , "float" . toCharArray ( ) , "int" . toCharArray ( ) , "long" . toCharArray ( ) , "short" . toCharArray ( ) , "void" . toCharArray ( ) } ; static final char [ ] classField = "class" . toCharArray ( ) ; static final char [ ] lengthField = "length" . toCharArray ( ) ; static final char [ ] THIS = "this" . toCharArray ( ) ; static final char [ ] THROWS = "throws" . toCharArray ( ) ; static InvocationSite FakeInvocationSite = new InvocationSite ( ) { public boolean isSuperAccess ( ) { } public boolean isTypeAccess ( ) { } public void setActualReceiverType ( ReferenceBinding receiverType ) { } public void setDepth ( int depth ) { } public void setFieldIndex ( int depth ) { } } ; public CompletionEngine ( ISearchableNameEnvironment nameEnvironment , ICompletionRequestor requestor , Map settings ) { } public void acceptClass ( char [ ] packageName , char [ ] className , int modifiers ) { } public void acceptInterface ( char [ ] packageName , char [ ] interfaceName , int modifiers ) { } public void acceptPackage ( char [ ] packageName ) { } public void acceptType ( char [ ] packageName , char [ ] typeName ) { } private void complete ( AstNode astNode , Binding qualifiedBinding , Scope scope ) { } public void complete ( IType type , char [ ] snippet , int position , char [ ] [ ] localVariableTypeNames , char [ ] [ ] localVariableNames , int [ ] localVariableModifiers , boolean isStatic ) { TypeConverter converter = new TypeConverter ( ) ; IType topLevelType = type ; while ( ( topLevelType . getDeclaringType ( ) ) != null ) { topLevelType = topLevelType . getDeclaringType ( ) ; } CompilationResult compilationResult = new CompilationResult ( ( ( topLevelType . getElementName ( ) ) + ".java" ) . toCharArray ( ) , 1 , 1 ) ; CompilationUnitDeclaration compilationUnit = new CompilationUnitDeclaration ( problemReporter , compilationResult , 0 ) ; <START_BUG> TypeDeclaration typeDeclaration = converter . buildCompilationUnit ( type , compilationUnit , compilationResult , problemReporter ) ; <END_BUG> if ( compilationUnit != null ) { AbstractMethodDeclaration fakeMethod = parseSnippetMethod ( snippet , position , localVariableTypeNames , localVariableNames , localVariableModifiers , isStatic ) ; AbstractMethodDeclaration [ ] oldMethods = typeDeclaration . methods ; AbstractMethodDeclaration [ ] newMethods = new AbstractMethodDeclaration [ ( oldMethods . length ) + 1 ] ; System . arraycopy ( oldMethods , 0 , newMethods , 0 , oldMethods . length ) ; newMethods [ oldMethods . length ] = fakeMethod ; typeDeclaration . methods = newMethods ; if ( CompletionEngine . DEBUG ) { System . out . println ( "SNIPPET<seq2seq4repair_space>COMPLETION<seq2seq4repair_space>AST<seq2seq4repair_space>:" ) ; System . out . println ( compilationUnit . toString ( ) ) ; } if ( ( compilationUnit . types ) != null ) { try { lookupEnvironment . buildTypeBindings ( compilationUnit ) ; if ( ( unitScope = compilationUnit . scope ) != null ) { lookupEnvironment . completeTypeBindings ( compilationUnit , true ) ; compilationUnit . scope . faultInTypes ( ) ; compilationUnit . resolve ( ) ; } } catch ( CompletionNodeFound e ) { if ( ( e . astNode ) != null ) { complete ( e . astNode , e . qualifiedBinding , e . scope ) ; } } } } } private AbstractMethodDeclaration parseSnippetMethod ( char [ ] snippet , int position , char [ ] [ ] localVariableTypeNames , char [ ] [ ] localVariableNames , int [ ] localVariableModifiers , boolean isStatic ) { } public void complete ( ICompilationUnit sourceUnit , int completionPosition , int offset ) { } private TypeBinding [ ] computeTypes ( Expression [ ] arguments , BlockScope scope ) { } private void findAnonymousType ( ReferenceBinding currentType , TypeBinding [ ] argTypes , Scope scope , InvocationSite invocationSite ) { } private void findClassField ( char [ ] token , TypeBinding receiverType ) { } private void findConstructors ( ReferenceBinding currentType , TypeBinding [ ] argTypes , Scope scope , InvocationSite invocationSite , boolean forAnonymousType ) { } private void findFields ( char [ ] fieldName , FieldBinding [ ] fields , Scope scope , ObjectVector fieldsFound , ObjectVector localsFound , boolean onlyStaticFields , ReferenceBinding receiverType , InvocationSite invocationSite , Scope invocationScope , boolean implicitCall ) { } private void findFields ( char [ ] fieldName , ReferenceBinding receiverType , Scope scope , ObjectVector fieldsFound , ObjectVector localsFound , boolean onlyStaticFields , InvocationSite invocationSite , Scope invocationScope , boolean implicitCall ) { } private void findFieldsAndMethods ( char [ ] token , TypeBinding receiverType , Scope scope , InvocationSite invocationSite , Scope invocationScope , boolean implicitCall ) { } private void findImports ( CompletionOnImportReference importReference ) { } private void findKeywords ( char [ ] keyword , char [ ] [ ] choices , Scope scope ) { } private void findMemberTypes ( char [ ] typeName , ReferenceBinding [ ] memberTypes , ObjectVector typesFound , ReferenceBinding receiverType , SourceTypeBinding invocationType ) { } private void findMemberTypes ( char [ ] typeName , ReferenceBinding receiverType , Scope scope , SourceTypeBinding typeInvocation ) { }

Fix:
TypeDeclaration typeDeclaration = converter . buildTypeDeclaration ( type , compilationUnit , compilationResult , problemReporter ) ;